Zinc battery elecrtolyte additive

ABSTRACT

An electrolyte additive is provided. The additive is a quaternary ammonium or phosphonium salt effective to suppress hydrogen evolution and metal dendrite formation during operation of a zinc electrochemical cell such as a zinc-air battery. A zinc battery cell is also provided, which contains an effective amount of the electrolyte additive.

This invention was made with government support under contract numberNSF 1746210 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

I. BACKGROUND OF THE INVENTION A. Field of Invention

The invention generally relates to chemical additives for zinc batteryelectrolytes.

B. Description of the Related Art

Despite their attractive cost and safety, batteries that utilize zinc astheir anode material suffer from several problems intrinsic to thismetal. Among these are 1) the formation of dendrites during rechargingand 2) parasitic side reactions such as the evolution of hydrogen gasfrom the electrolyte reacting at the zinc surface. These problems havecontributed to both limit the penetration of zinc batteries into certainmarkets and to prevent the emergence of otherwise promising zinc batterychemistries such as Zinc-Air. Dendrite formation reduces batteryefficiency and can lead to cell failure. Hydrogen evolution can causereduced shelf life due to self-discharge as well as mechanical damagedue to pressure buildup. It is known to use additives to suppressdendrite formation and hydrogen evolution; however, few known additivesare effective at suppressing dendrite formation and hydrogen evolution.Moreover, known additives exhibit certain negative properties such asloss of cell efficiency. Some embodiments of the present invention mayprovide one or more benefits or advantages over the prior art.

II. SUMMARY OF THE INVENTION

Embodiments of the invention may relate to electrolyte additives forpartially or fully suppressing dendrite formation and hydrogen evolutionin zinc batteries. Embodiments include a zinc electrochemical batterycell incorporating the additives. Embodiments also include electrolyteadditive chemical compositions comprising quaternary ammonium orphosphonium salts.

As used herein the terms “embodiment”, “embodiments”, “someembodiments”, “other embodiments” and so on are not exclusive of oneanother. Except where there is an explicit statement to the contrary,all descriptions of the features and elements of the various embodimentsdisclosed herein may be combined in all operable combinations thereof.

Language used herein to describe process steps may include words such as“then” which suggest an order of operations; however, one skilled in theart will appreciate that the use of such terms is often a matter ofconvenience and does not necessarily limit the process being describedto a particular order of steps.

Conjunctions and combinations of conjunctions (e.g. “and/or”) are usedherein when reciting elements and characteristics of embodiments;however, unless specifically stated to the contrary or required bycontext, “and”, “or” and “and/or” are interchangeable and do notnecessarily require every element of a list or only one element of alist to the exclusion of others.

Terms of degree, terms of approximation, and/or subjective terms may beused herein to describe certain features or elements of the invention.In each case sufficient disclosure is provided to inform the personhaving ordinary skill in the art in accordance with the writtendescription requirement and the definiteness requirement of 35 U.S.C.112.

The term “effective amount” is used herein to indicate an amount of anelectrolyte additive dissolved in a liquid electrolyte that reducesdendrite formation and hydrogen evolution by a measurable and/orvisually perceptible amount under the stated test conditions, or whereno conditions are stated in 4M potassium hydroxide, 0.1M zinc oxide, andwater at −1.6V relative to a Hg/HgO reference electrode for 1500seconds. However, this is not intended to limit the invention to thestated test conditions. The person having ordinary skill in the artwould readily understand that a wide variety of electrolytes andconcentrations of electrolytes, for instance, may be appropriate ordesirable for a given application. It is well within the skill in theart to select from known electrolytes.

III. BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangement ofparts, embodiments of which will be described in detail in thisspecification and illustrated in the accompanying drawings which form apart hereof, wherein like reference numerals indicate like structure,and wherein:

FIG. 1 is a photograph of electrodeposited zinc in a control cellcontaining no additive after operating the cell for 1500 s;

FIG. 2 is a photograph of electrodeposited zinc in a cell containing 1.0wt % Benzyltrimethylammonium Hydroxide after operating the cell for 1500s;

FIG. 3 is a photograph of electrodeposited zinc in a cell containing 1.0wt % Benzyltributylammonium Chloride after operating the cell for 1500s;

FIG. 4 is a photograph of electrodeposited zinc in a cell containing 1.0wt % Dibenzyldimethylammonium Chloride after operating the cell for 1500s;

FIG. 5 is a photograph of electrodeposited zinc in a cell containing0.01 wt % Dibenzyldimethylammonium Chloride after operating the cell for1500 s;

FIG. 6 is a photograph of electrodeposited zinc in a cell containing 0.1wt % Dibenzyldimethylammonium Chloride after operating the cell for 1500s;

FIG. 7 is ¹H NMR data for 1-(Trimethylammonium methyl)naphthalenechloride in D₂O with an inlay photograph of electrodeposited zinc in acell containing 1.0 wt % 1-(Trimethylammonium methyl)naphthalenechloride after operating the cell for 1500 s;

FIG. 8 is ¹H NMR data for 4-(Trimethylammonium methyl)benzonitrileChloride in D₂O with an inlay photograph of electrodeposited zinc in acell containing 1.0 wt % 4-(Trimethylammonium methyl)benzonitrileChloride after operating the cell for 1500 s;

FIG. 9 is a photograph of electrodeposited zinc in a cell containing 1.0wt % 4-(Trimethylammonium methyl)anisole Chloride after operating thecell for 1500 s;

FIG. 10 is a photograph of electrodeposited zinc in a cell containing0.5 wt % 4-(Trimethylammonium methyl)anisole Chloride after operatingthe cell for 1500 s;

FIG. 11 is a photograph of electrodeposited zinc in a cell containing0.1 wt % 4-(Trimethylammonium methyl)anisole Chloride after operatingthe cell for 1500 s;

FIG. 12 is a photograph of electrodeposited zinc in a cell containing1.0 wt % 4-(Trimethylammonium methyl)-1,2,6-trimethoxybenzene afteroperating the cell for 1500 s;

FIG. 13 is a photograph of electrodeposited zinc in a cell containing1.0 wt % (4-Methylbenzyl)trimethylammonium Chloride after operating thecell for 1500 s;

FIG. 14 is ¹H NMR data for (2-Methylbenzyl)trimethylammonium Chloride inD₂O with an inlay photograph of electrodeposited zinc in a cellcontaining 1.0 wt % (2-Methylbenzyl)trimethylammonium Chloride afteroperating the cell for 1500 s;

FIG. 15 is a photograph of electrodeposited zinc in a cell containing1.0 wt % (4-Chlorobenzyl)trimethylammonium Chloride after operating thecell for 1500 s;

FIG. 16 is ¹H NMR data for (2-Chlorobenzyl)trimethylammonium Chloride inD₂O with an inlay photograph of electrodeposited zinc in a cellcontaining 1.0 wt % (2-Chlorobenzyl)trimethylammonium Chloride afteroperating the cell for 1500 s;

FIG. 17 is ¹H NMR data for (4-Bromobenzyl)trimethylammonium Bromide inD₂O with an inlay photograph of electrodeposited zinc in a cellcontaining 1.0 wt % (4-Bromobenzyl)trimethylammonium Bromide afteroperating the cell for 1500 s;

FIG. 18 is ¹H NMR data for Benzyltrimethylphosphonium Chloride in D₂Owith an inlay photograph of electrodeposited zinc in a cell containing1.0 wt % Benzyltrimethylphosphonium Chloride after operating the cellfor 1500 s;

FIG. 19 is a photograph of electrodeposited zinc in a cell containing1.0 wt % (2-Hydroxybenzyl)trimethylammonium Iodide after operating thecell for 1500 s;

FIG. 20 is ¹H NMR data for (3-Methylbenzyl)trimethylammonium Chloride inD₂O with an inlay photograph of electrodeposited zinc in a cellcontaining 1.0 wt % (3-Methylbenzyl)trimethylammonium Chloride afteroperating the cell for 1500 s;

FIG. 21 is ¹H NMR data for 4-(Trimethylammonium)benzoic acid Bromide inD₂O with an inlay photograph of electrodeposited zinc in a cellcontaining 1.0 wt % 4-(Trimethylammonium methyl)benzoic acid Bromideafter operating the cell for 1500 s;

FIG. 22 is a photograph of electrodeposited zinc in a cell containing1.0 wt % 3-(Trimethylammonium methyl)anisole Chloride after operatingthe cell for 1500 s;

FIG. 23 is a photograph of electrodeposited zinc in a cell containing1.0 wt % Benzalkonium Chloride after operating the cell for 1500 s;

FIG. 24 is ¹H NMR data for (2,6-Dimethylbenzyl)trimethylammoniumChloride in D₂O with an inlay photograph of electrodeposited zinc in acell containing 1.0 wt % (2,6-Dimethylbenzyl)trimethylammonium;

FIG. 25 is a photograph of electrodeposited zinc in a cell containing 25wt % Benzyltrimethylammonium chloride after operating the cell for 1500s;

FIG. 26 is ¹H NMR data for (2,6-Dichlorobenzyl)trimethylammoniumchloride in D₂O;

FIG. 27 is ¹H NMR data for (3,4-Dimethylbenzyl)trimethylammoniumchloride in D₂O with an inlay photograph of electrodeposited zinc in acell containing 1.0 wt % (3,4-Dimethylbenzyl)trimethylammonium chlorideafter operating the cell for 1500 s;

FIG. 28 is ¹H NMR data for (4-Hydroxybenzyl)trimethylammonium Iodide inD₂O;

FIG. 29 is a photograph of electrodeposited zinc in a cell containing 15wt % 4-(Trimethylammoniummethyl)anisole chloride after operating thecell for 1500 s;

FIG. 30 is a photograph of electrodeposited zinc in a cell containing 15wt % (4-Methylbenzyl)trimethylammonium chloride after operating the cellfor 1500 s;

FIG. 31 is a photograph of electrodeposited zinc in a cell containing0.1 wt % (4-Methylbenzyl)trimethylammonium chloride after operating thecell for 1500 s; and

FIG. 32 is a schematic view of a general zinc-based battery inaccordance with one or more embodiments of the invention.

IV. DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention include organic electrolyte additives thatimprove zinc battery performance by both selectively preventing dendriteformation and preventing hydrogen evolution side reactions withouthindering cell efficiency. Embodiments may include quaternary nitrogenand/or quaternary phosphorous compounds substituted with a variety oflinear and/or cyclic organic groups.

Formula I illustrates an embodiment of the invention comprising acentral nitrogen or phosphorous atom with a charge of +1, denoted hereinas “N/P⁺” or as an “N/P⁺ center”. The N/P⁺ center is bonded to four Rgroups R¹, R², R³, and R⁴. The structure shown in Formula I is notintended to illustrate isomers or stereochemical structures, but ratheris intended to encompass all isomeric forms with the same atom-to-atomconnectivity.

R¹ is selected from the following radicals, where “yl” or “methylene”refers to the position of the radical electron available for bondingwith an N/P+ center: methyl benzene, 4-methylene-toluene,3-methylene-toluene, 2-methylene-toluene, 4-methylene-chlorobenzene,3-methylene-chlorobenzene, 2-methylene-chlorobenzene,4-methylene-bromobenzene, 3-methylene-bromobenzene,2-methylene-bromobenzene, 4-methylene-iodobenzene,3-methylene-iodobenzene, 2-methylene-iodobenzene,4-methylene-cyanobenzene, 3-methylene-cyanobenzene,2-methylene-cyanobenzene, 4-methylene-anisole, 3-methylene-anisole,2-methylene-anisole, 1-methylnaphthalene,1-methylene-2,6-dimethylbenzene, 1-methylene-2,4-dimethylebenzene,1-methylene-3,4-dimethylbenzene, 1-methylene-2,5-dimethylbenzene,1-methylene-3,5-dimethylbenzene, 1-methylene-2,4,6-trimethylbenzene,1-methylene-3,4,5-trimethoxybenzene, 1-methylene-2,6-dichlorobenzene,4-methylene-nitrobenzene, 4-methylene-benzoic acid, 3-methylene-benzoicacid, 2-methylene-benzoic acid, 2-methylene-phenol, 3-methylene-phenol,and 4-methylene-phenol.

With continuing reference to Formula I, the radicals R², R³, and R⁴ maybe independently selected from R¹, methyl, ethyl, n-propyl, n-butyl,n-pentyl, n-hexyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl,n-hexadecyl, or n-octadecyl. Radicals R², R³, and R⁴ may beindependently selected from linear and non-linear alkyls from C1 to C25.

Embodiments conforming to Formula I may include a sufficient amount ofcounter anion [An] to produce a neutral species. The anion [An] may be,for example and without limitation, chloride, bromide, iodide, fluoride,hydroxide, nitrate, nitrite, sulphate, sulphite, phosphate, perchlorate,or any combination thereof. The person having ordinary skill in the artwill readily appreciate that the anion has less or no influence onperformance of the electrolyte additives of the present invention.Accordingly, a wide variety of anions are within the scope of theinvention, and the foregoing list is meant only to be illustrative.

Referring now to the drawings wherein the showings are for purposes ofillustrating embodiments of the invention only and not for purposes oflimiting the same, FIG. 1 is a photograph showing dendrite growth using4M KOH, 0.1M ZnO, and water with no additives suppressing dendritegrowth. Plating was conducted at −1.6V relative to a Hg/HgO referenceelectrode for 1500 seconds. FIG. 1 shows dendrite growth after 1500seconds. This serves as a control against which dendrite suppressionadditives are compared in subsequent tests. Each experimental run isconducted under the same conditions as the control run, namely, in 4MKOH electrolyte, 0.1M ZnO, and water at −1.6V relative to a Hg/HgOreference electrode for 1500 seconds. The results are summarized inTable I.

With respect to the control results shown in FIG. 1, prominent dendritegrowth is clearly visible. Although the control rapidly evolveshydrogen, the bubbles form so quickly over the entire surface that theydo not adhere to the dendrites. Accordingly, very few if any hydrogenbubbles are visible in FIG. 1. In contrast FIGS. 2-18 all showsuppression of hydrogen evolution to some degree, which may be completehydrogen suppression or partial hydrogen suppression. Where hydrogensuppression is complete, no bubbles form on the plated zinc surface sothe associated figure shows no hydrogen bubbles. However, where hydrogenevolution is partially suppressed large slow-forming hydrogen bubblesare visible in the associated figure adhering to the plated zinc.

TABLE I Suppression of Dendrite Formation by Additives Amount HydrogenDendrite Additive (wt %) Suppressed Suppressed Figure No additive(control) 0 No No Fig. 1 Benzyltrimethylammonium Hydroxide 1.0 PartialYes Fig. 2

Benzyltributylammonium Chloride (BTBAC) 1.0 Partial Yes Fig. 3

Dibenzyldimethylammonium Chloride 1.0 Partial Yes Fig. 4 (DBDMAC)

Dibenzyldimethylammonium Chloride 0.01 No Partial Fig. 5 (DBDMAC)Dibenzyldimethylammonium Chloride 0.1 Partial Yes Fig. 6 (DBDMAC)1-(Trimethylammonium methyl)naphthalene 1.0 No Partial Fig. 7 Chloride(TMAMNC)

4-(Trimethylammoniummethyl)benzonitrile 1.0 Yes Partial Fig. 8 Chloride(TMAMBC)

4-(Trimethylammoniummethyl)anisole 1.0 Yes Yes Fig. 9 Chloride

4-(Trimethylammoniummethyl)anisole 0.5 Partial Yes Fig. 10 Chloride4-(Trimethylammoniummethyl)anisole 0.1 Partial Partial Fig. 11 Chloride4-(Trimethylammoniummethyl)-1,2,6- 1.0 Partial Yes Fig. 12trimethoxybenzene

(4-Methylbenzyl)trimethylammonium Chloride 1.0 Partial Yes Fig. 13

(4-Methylbenzyl)trimethylammonium 15 Yes Yes Fig. 30 chloride(4-Methylbenzyl)trimethylammonium 0.1 Partial Partial Fig. 31 chloride(2-Methylbenzyl)trimethylammonium Chloride 1.0 Partial Yes Fig. 14

(4-Chlorobenzyl)trimethylammonium Chloride 1.0 Partial Partial Fig. 15

(2-Chlorobenzyl)trimethylammonium Chloride 1.0 No Partial Fig. 16

(4-Bromobenzyl)trimethylammonium Bromide 1.0 Partial Yes Fig. 17

Benzyltrimethylphosphonium Chloride 1.0 No Partial Fig. 18

(2-Hydroxybenzyl)trimethylammonium Iodide 1.0 Partial Partial Fig. 19

(3-Methylbenzyl)trimethylammonium Chloride 1.0 Partial Yes Fig. 20

4-(Trimethylammoniummethyl)benzoic acid 1.0 Partial Partial Fig. 21Bromide

3-(Trimethylammoniummethyl)anisole 1.0 Partial Partial Fig. 22 Chloride

Benzalkonium Chloride 1.0 Partial Yes Fig. 23

(2,6-Dimethylbenzyl)trimethylammonium 1.0 No Partial Fig. 24 Chloride

Benzyltrimethylammonium Hydroxide 25 Yes Yes Fig. 25 (BTMAH)

(2,6-Dichlorobenzyl)trimethylammonium 1.0 Partial No Fig. 26 Chloride

(3,4-Dimethylbenzyl)trimethylammonium 1.0 Yes Yes Fig. 27 Chloride

(4-Hydroxybenzyl)trimethylammonium Iodide 1.0 Partial Partial Fig. 28

4-(Trimethylammoniummethyl)anisole 15 Yes Yes Fig. 29 Chloride

Dibenzylimethylammonium chloride (DBDMAC) preparation and performance.

N,N-dimethylbenzylamine (2 g, 14.8 mmol) is diluted into 10 mL ofacetonitrile and stirred under air. Benzylchloride (2.06 g, 1.87 mL,16.3 mmol) is added at once and the reaction is heated to 78° C. toreflux for 3 hours. The solution is concentrated under reduced pressureto a colorless viscous oil. The desired product is recrystallized fromacetone. A white/colorless crystal solid of 3.50 g is collected (90.4%yield) and its structure is confirmed by ¹H NMR. The dendritesuppressive effect of this additive is shown in FIGS. 4-6. Full dendritesuppression occurs at 1 wt % and 0.1 wt %, and partial suppression isobserved at 0.01 wt %. Hydrogen evolution is partially suppressed at 1wt % and 0.1 wt %. No hydrogen suppression is observed at 0.01 wt %.

1-(Trimethylammonium methyl)naphthalene chloride preparation andperformance.

To a 100 mL flask is added 10 mL of a 13% solution of trimethylamine intetrahydrofuran (1.16 g, 19.7 mmol). The solution is stirred under airat room temperature. 1-(Chloromethyl)naphthalene (3.80 g, 3.22 mL, 21.5mmol) is added in four quick portions and the reaction is heated to 60°C. for 3 hours. The reaction is then cooled to room temperature andwhite precipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 3.10 g of white fluffy powder iscollected (67% yield), and the desired product structure is confirmed by¹H NMR. The partial dendrite suppressive effect of this additive isshown in FIG. 7. 1-(Trimethylammonium methyl)naphthalene chloridepromotes, rather than suppresses, hydrogen evolution.

4-(Trimethylammoniummethyl)benzonitrile chloride preparation andperformance.

To a 100 mL flask is added 10 mL of a 13% solution of trimethylamine intetrahydrofuran (1.16 g, 19.7 mmol). The solution is stirred under airat room temperature. 4-(Chloromethyl)benzonitrile (2.70 g, 17.8 mmol) isadded in quick portions and the reaction is heated to 60° C. for 2hours. The reaction is then cooled to room temperature and whiteprecipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 2.80 g of white fluffy powder iscollected (75% yield), and the desired product structure is confirmed by¹H NMR. The partial dendrite suppressive effect of this additive isshown in FIG. 8. This additive strongly suppresses hydrogen evolution.

4-(Trimethylammoniummethyl)anisole chloride preparation and performance.

To a 100 mL flask is added 20 mL of a 13% solution of trimethylamine intetrahydrofuran (2.32 g, 39.4 mmol) and this is stirred under air atroom temperature. (4-Methoxybenzyl)chloride (5.59 g, 4.84 mL, 35.7 mmol)is added in quick portions and the reaction is heated to 60° C. for 3hours. The reaction is then cooled to room temperature and whiteprecipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 7.08 g of white fluffy powder iscollected (92% yield) and the desired product structure is confirmed by¹H NMR. The dendrite suppressive effect of this additive is shown inFIGS. 9-11. Dendrite suppression is complete under the test conditionsat 1 wt % and 0.5 wt %, and partial at 0.1 wt %. Hydrogen evolution isfully suppressed at 1.0 wt % and partially suppressed at 0.5 wt % and0.01 wt %.

An analogous method is used to synthesize3-(trimethylammoniummethyl)anisole chloride, as well as similar4-(trimethylammoniummethyl)-1,2,6-trimethoxybenzene. FIG. 12 shows that4-(trimethylammoniummethyl)-1,2,6-trimethoxybenzene fully suppressesdendrite formation under the test conditions at 1.0 wt %, and partiallysuppresses hydrogen evolution. FIG. 22 shows that3-(trimethylammoniummethyl)anisole chloride fully suppresses hydrogenevolution and dendrite formation.

(4-Methylbenzyl)trimethylammonium chloride preparation and performance.

To a 100 mL flask is added 10 mL of a 13% solution of trimethylamine intetrahydrofuran (1.16 g, 19.7 mmol). The solution is stirred under airat room temperature. 4-Methylbenzyl chloride (2.75 g, 2.6 ml, 19.5 mmol)is added in quick portions and the reaction is heated to 60° C. for 3hours. The reaction is then cooled to room temperature and whiteprecipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 2.92 g of white fluffy powder iscollected (75% yield) and the desired product structure is confirmed by¹H NMR. FIG. 13 shows that 1 wt % (4-methylbenzyl)trimethylammoniumchloride fully suppresses dendrite formation under the test conditions,and partially suppresses hydrogen evolution. FIG. 30 shows that 15 wt %(4-methylbenzyl)trimethylammonium chloride fully suppresses dendriteformation and hydrogen evolution under the test conditions. FIG. 31shows that 0.1 wt % (4-methylbenzyl)trimethylammonium chloride partiallysuppresses dendrite formation, and less effective in suppressinghydrogen evolution than higher tested concentrations of this additive.

(3,4-dimethylbenzyl)trimethylammonium chloride preparation andperformance.

To a 100 mL flask is added 10.0 ml of a 13% solution of trimethylaminein tetrahydrofuran (1.16 g, 19.6 mmol). The solution is stirred underair at room temperature. 3,4-Dimethylbenzyl chloride (2.75 g, 17.8 mmol)is added in quick portions and the reaction is heated to 60° C. for 4hrs. The reaction is then cooled to room temperature and whiteprecipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 2.75 g of white fluffy powder arecollected (73% yield) and the desired product structure is confirmed by¹H NMR as shown in FIG. 27. Also shown in FIG. 27 is an inlay photoshowing that 1.0 wt % (3,4-dimethylbenzyl)trimethylammonium chloridefully suppresses dendrite formation and fully suppresses hydrogenevolution under the test conditions.

An analogous method is used to synthesize other isomers of this product,namely, (2-methylbenzyl)trimethylammonium chloride and(3-methylbenzyl)trimethylammonium chloride, as well as(2,4-dimethylbenzyl)trimethylammonium chloride,(2,5-dimethylbenzyl)trimethylammonium chloride,(2,6-dimethylbenzyl)trimethylammonium chloride,(3,5-dimethylbenzyl)trimethylammonium chloride, and(2,4,6-trimethylbenzyl)trimethylammonium chloride. FIG. 14 shows that 1wt % (2-methylbenzyl)trimethylammonium chloride fully suppressesdendrite formation, and partially suppresses hydrogen evolution. FIG. 20shows that 1 wt % (3-methylbenzyl)trimethylammonium chloride partiallysuppresses dendrite formation, and partially suppresses hydrogenevolution, under the test conditions.

(4-Chlorobenzyl)trimethylammonium chloride preparation and performance.

To a 100 mL flask is added 10 mL of a 13% solution of trimethylamine intetrahydrofuran (1.16 g, 19.7 mmol). The solution is stirred under airat room temperature. 4-Chlorobenzyl chloride (2.86 g, 17.8 mmol) isadded in quick portions and the reaction is heated to 60° C. for 3hours. The reaction is then cooled to room temperature and the whiteprecipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 3.17 g of white fluffy powder arecollected (82% yield) and the desired product structure is confirmed by¹H NMR. FIG. 15 shows that 1 wt % (4-chlorobenzyl)trimethylammoniumchloride partially suppresses dendrite formation, and hydrogenevolution, under the test conditions.

An analogous method is used to synthesize(2-chlorobenzyl)trimethylammonium chloride,(3-chlorobenzyl)trimethylammonium chloride,(2-bromobenzyl)trimethylammonium bromide,(3-bromobenzyl)trimethylammonium bromide, and(4-bromobenzyl)trimethylammonium bromide, with the later three usingreagent bromobenzyl bromide in place of chlorobenzyl chloride.Similarly, iodobenzyl chlorides are used in an analogous method toproduce (2-iodobenzyl)trimethylammonium chloride,(3-bromobenzyl)trimethylammonium chloride, and(4-iodobenzyl)trimethylammonium chloride. FIG. 16 shows that(2-chlorobenzyl)trimethylammonium chloride does not suppress dendriteformation under the test conditions, but does partially suppresshydrogen evolution. FIG. 17 shows that 1 wt %(4-bromobenzyl)trimethylammonium bromide fully suppresses dendriteformation under the test conditions, and partially suppress hydrogenevolution.

Benzyltrimethylphosphonium chloride preparation and performance.

To a 100 mL flask is added 10 mL of a 1M solution of trimethylphosphinein tetrahydrofuran (1.52 g, 20, ml, 20 mmol). The solution is stirredunder nitrogen at room temperature. Benzylchloride (2.52 g, 2.3 ml, 20.0mmol) is added in quick portions and the reaction is heated to 60° C.for 3 hours. The reaction is then cooled to room temperature and whiteprecipitates are collected by brief suction filtration. About 1.80 g ofwhite fluffy powder is collected (44% yield) and the desired productstructure is confirmed by ¹H NMR. FIG. 18 shows that 1 wt %benzyltrimethylphosphonium chloride partially suppresses dendriteformation, but does not suppress hydrogen evolution, under the testconditions.

(2-Hydroxybenzyl)trimethylammonium iodide preparation and performance.

To a 100 mL flask is added 2-[(Dimethylamino)methyl]phenol (2.45 g, 16.2mmol) and tetrahydrofuran (25 mL). The clear solution is cooled to 0° C.by an ice bath under air and with magnetic stirring. To this solutioniodomethane (3.45 g, 24.3 mmol) is added dropwise. After stirring for 20minutes the ice bath is removed and the reaction proceeds at roomtemperature for 3 hours as a viscous oil forms at the bottom of theflask. The solvents are removed from the reaction by reduced pressure(Rotavap) to a mass of orange/brown amorphous solid measuring 4.6 g (94%yield). The desired product structure is confirmed by ¹H NMR. FIG. 19shows that 1 wt % (2-hydroxybenzyl)trimethylammonium iodide partiallysuppresses dendrite formation, and partially suppresses hydrogenevolution, under the test conditions.

4-(Trimethylammoniummethyl)benzoic acid bromide preparation.

To a 100 mL flask is added 8.0 mL of a 13% solution of trimethylamine intetrahydrofuran (0.92 g, 15.6 mmol) is diluted in 30 mL acetonitrile.The solution is stirred under air at room temperature. Then,4-(bromomethyl)benzoic Acid (3.36 g, 15.6 mmol) is added in quickportions and the reaction is heated to 80° C. for 3 hrs. The reaction isthen cooled to room temperature and white precipitates are collected bysuction filtration and washed with additional tetrahydrofuran. About4.10 g of white solids are collected (95.6% yield) and the desiredproduct structure is confirmed by ¹H NMR. FIG. 21 shows that 1 wt %4-(Trimethylammoniummethyl)benzoic acid bromide partially suppressesdendrite formation, and partially suppresses hydrogen evolution, underthe test conditions.

(2,6-Dimethylbenzyl)trimethylammonium chloride preparation.

To a 100 mL flask is added 9.1 mL of a 13% solution of trimethylamine intetrahydrofuran (1.05 g, 17.8 mmol). The solution is stirred under airat room temperature. 2,6-Dimethylbenzyl chloride (2.5 g, 16.2 mmol) isadded in quick portions and the reaction is heated to 60° C. for 3 hrs.The reaction is then cooled to room temperature and the whiteprecipitates are collected by suction filtration and washed withadditional tetrahydrofuran. About 3.05 g of white fluffy powder arecollected (88% yield) and the desired product structure is confirmed by¹H NMR. FIG. 24 shows that 1.0 wt %(2,6-Dimethylbenzyl)trimethylammonium chloride partially suppressesdendrite formation, but does not suppress hydrogen evolution, under thetest conditions.

FIG. 23 shows that 1.0 wt % Benzalkonium Chloride is effective in fullysuppressing dendrite formation and hydrogen evolution under the testcondition. The tested additive is a mixture having the followingformula, where R⁵=C_(n)H_(2n+1) where 8≤n≤18:

FIG. 32 shows a schematic view of a zinc-battery cell 100. The cellincludes a zinc anode 102 in communication with a cathode 108 through anelectrolyte 104. A porous separator 110 such as a membrane may beinterposed between the cathode 108 and the electrolyte 104. The personhaving ordinary skill in the art will readily appreciate that thecathode may comprise a wide variety of known materials such as withoutlimitation, air and carbon.

It will be apparent to those skilled in the art that the above methodsand apparatuses may be changed or modified without departing from thegeneral scope of the invention. The invention is intended to include allsuch modifications and alterations insofar as they come within the scopeof the appended claims or the equivalents thereof.

Having thus described the invention, it is now claimed:

1. A composition, comprising:

wherein, N/P is a central nitrogen atom having a +1 charge; wherein R¹is selected from the group consisting of 2 methylene-chlorobenzene, 3methylene-bromobenzene, 2-methylene-bromobenzene,4-methylene-cyanobenzene, 3-methylene-cyanobenzene,2-methylene-cyanobenzene, 1 methylene-2,4-dimethylbenzene,1-methylene-3,4-dimethylbenzene, 1-methylene-2,5-dimethylbenzene, 3-methylene-benzoic acid, 2-methylene-benzoic acid, 2-methylene-phenol,3-methylene-phenol, and 2 methylene-anisole; and wherein [An]− is acounter anion.
 2. The composition of claim 1, wherein N/P is phosphorousand R1 is methylene benzene.
 3. The composition of claim 1, wherein thecounter anion is selected from chloride, bromide, iodide, fluoride,hydroxide, nitrate, nitrite, sulphate, sulphite, phosphate, perchlorate,or any combination thereof.
 4. A composition, comprising:

wherein, N/P is a central phosphorous atom having a +1 charge; whereinR¹ is selected from the group consisting of 3-methylene-toluene,2-methylene-toluene, 3-methylene-chlorobenzene,2-methylene-chlorobenzene, 4-methylene-bromobenzene,3-methylene-bromobenzene, 2-methylene-bromobenzene,4-methylene-cyanobenzene, 3-methylene-cyanobenzene,2-methylene-cyanobenzene, 1-methylnaphthalene,1-methylene-2,6-dimethylbenzene, 1-methylene-2,4-dimethylbenzene,1-methylene-3,4-dimethylbenzene, 1-methylene-2,5-dimethylbenzene,1-methylene-3,5-dimethylbenzene, 1-methylene-2,6-dichlorobenzene,4-methylene-benzoic acid, 3-methylene-benzoic acid, 2-methylene-benzoicacid, 2-methylene-phenol, 3-methylene-phenol, 4-methylene-phenol,4-methylene-anisole, 3-methylene-anisole, 2-methylene-anisole; andwherein [An]− is a counter anion.
 5. The composition of claim 4, whereinR1 is methylene benzene.
 6. The composition of claim 4, wherein thecounter anion is selected from chloride, bromide, iodide, fluoride,hydroxide, nitrate, nitrite, sulphate, sulphite, phosphate, perchlorate,or any combination thereof.